Closed-cell elastomeric foams are used not only as thermal insulators but also as water vapor retardants on cold surfaces. The article discusses the extent to which refrigeration and air conditioning systems are protected by these materials against moisture absorption.

A balance has to be struck between the complexity of the models used to represent the heat transfer mechanisms and the amount of experimental information and the associated accuracy of information needed to verify these models. The solid, gas and radiation contributions can be treated as uncoupled, yet such a treatment can reasonably represent the heat transfer through foams. The solid contribution is a strong function of how the polymer is distributed between struts and cell walls, and the density of the foam. The radiation heat transfer through foams can be represented by diffusion approximation, and it is mostly absorption dominated. Therefore, measurement of the extinction coefficient is sufficient for adequate representation. The higher the extinction coefficient, the lower is the radiation contribution.

Wide usage of cellular foam as low temperature thermal insulating material warrants good understanding of its thermal and water vapor transmission behavior. An attempt has been made to experimentally observe the effect of cell shape on heat and mass transfer characteristics of cellular foams. The foam samples used in this study were derived from elastomeric foam The thermal conductivity and water vapor transmission data were taken on foams with three different cell shapes. one having spherical cells and two having elliptical cells, with varied degree of elongation.The thermal conductivity measurements on the samples described above were obtained using Thin-Heater thermal conductivity apparatus, otherwise known as the ASTM C-1114 test. The thermal measurements were performed in the temperature range of 35 to 153°F. The experimental data indicated no significant effect of the cell elongation on thermal conductivity of foam. This could be attributed to the following : a) the densities of the foam were roughly the same, and therefore conduction heat transfer was not significantly changed; b) the possible decrease in the radiation component of thermal conductivity because of elongated cells was nullified by the increase in transmission of heat attributable to relatively thinner walls resulting from the stretching of the foams during sample preparation. Additionally, the change in the shape of cells could have changed the radiation heat transfer characteristic of the samples.Water vapor permeabilities of the foams with elongated cells were measured with Permatran® and compared to that of the foam with uniform cells. It was found that the foams with elongated cells had almost twice the permeability as the foams with uniform cells Also, the two foams with elongated cells had about the same perme-

Mats are often composites of fibers and filler particulates. They are formed by draining a dilute aqueous slurry on a filter medium called ''forming fabric'', consolidated and dried. In general, formation of non-woven fibrous mats containing fibers and inorganic filler particulates is strongly influenced by the drainage characteristics of the slurry. These characteristics depend on chemical additives as well as physical properties of the slurry constituents -for example size distribution of fibers and fillers. The qualities of resulting mats, such as wet strength and water load, are important control parameters from the viewpoint of process runnability and efficiency. Proper control of mat quality parameters allows one to enhance productivity through scrap reduction. Using on-line slurry analyzer data in combination with the processing variables of the forming section, we can obtain estimates of mat quality parameters in real-time through applications of neural networks. We use neural networks to identify nonparametric functional approximations for predictive process modeling. This paper deals with real-time prediction of wet mat quality using on-line monitoring of slurry characteristics. This is significant as it allows one to obtain a product property that is normally available from destructive laboratory tests only.

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